M4: Insufficient Input/Output Validation – OWASP Mobile Top 10 – Best Practices


In the 2023 edition of the OWASP Mobile Top 10, Insufficient Input/Output Validation secured the 4th position. This blog aims to shed light on the implications of this vulnerability, explore a real-world example, and discuss effective mitigation techniques to safeguard mobile applications.

In the ever-evolving landscape of cybersecurity, mobile applications are becoming an integral part of our daily lives. With the increasing reliance on mobile devices, the security of mobile applications is of paramount importance. The Open Web Application Security Project (OWASP) recognizes this significance and regularly updates its Mobile Top 10 list to highlight the most critical security risks in mobile applications.

Understanding Insufficient Input/Output Validation

Insufficient Input/Output Validation occurs when a mobile application fails to properly validate and sanitize user inputs and outputs. In simple terms, if an application doesn’t thoroughly check and filter the data it receives from users and the data it sends back to users, it becomes vulnerable to a range of attacks.

Real-world Example: E-commerce Application Price Tampering

Consider a popular e-commerce mobile application that allows users to search for products and view their prices. This application lets users filter products based on price ranges to find items within their budget. The application uses a simple backend API to fetch product information based on user queries.

Now, if this application lacks proper input validation and sanitization, an attacker could exploit this vulnerability to tamper with product prices, leading to potential financial losses and damage to the reputation of the e-commerce platform.

Exploitation Scenario: Price Manipulation

Normal User Interaction:

A legitimate user searches for smartphones in the price range of $500 to $800.

Attacker’s Malicious Input:

The attacker, however, intercepts the communication between the mobile app and the backend API. Using a tool like Burp Suite, they manipulate the search query to include additional parameters not validated by the application. /api/products?category=smartphones&min_price=500&max_price=800

The attacker modifies the request to: /api/products?category=smartphones&min_price=1&max_price=1; DROP TABLE Products --

Insufficient Validation:

Due to insufficient input validation, the backend API fails to properly sanitize the input and constructs an SQL query using the manipulated price range.

SELECT * FROM Products WHERE category='smartphones' AND price BETWEEN 1 AND 1; DROP TABLE Products --

SQL Injection Attack:

The injected SQL code causes the database to retrieve products with prices between 1 and 1, effectively returning a broader set of results. In the worst case, the “Products” table could be dropped, leading to a loss of all product information.


The attacker can now see a wide range of products, including those with significantly reduced prices. They could proceed to purchase high-value items at these manipulated prices, causing financial harm to both the e-commerce platform and the legitimate users.

Implications of Insufficient Input/Output Validation:

  1. Data Manipulation and Theft: Attackers can manipulate input data to gain unauthorized access, modify sensitive information, or steal confidential data.
  2. Command Execution: Without proper validation, attackers may inject malicious commands into the input, leading to the execution of unintended operations on the server.
  3. Denial of Service (DoS): Inadequate validation can be exploited to flood the application with malicious inputs, causing it to become unresponsive and leading to a denial of service.

Mitigation Techniques:

  1. Input Validation:
    • Implement strict input validation by defining and enforcing proper data formats.
    • Use input validation libraries and frameworks to automatically filter out malicious inputs.
  2. Parameterized Queries:
    • Utilize parameterized queries or prepared statements to prevent SQL injection attacks.
    • Avoid constructing SQL queries by concatenating user inputs.
  3. Output Encoding:
    • Encode output data to prevent Cross-Site Scripting (XSS) attacks.
    • Use secure coding practices and frameworks that automatically handle output encoding.
  4. Data Whitelisting:
    • Employ whitelisting techniques to only allow known and expected data inputs.
    • Restrict input to a predefined set of characters or patterns.
  5. Regular Security Audits:

Wrapping Up

Insufficient Input/Output Validation poses a significant threat to the security of mobile applications. By understanding the risks and implementing effective mitigation techniques, developers can fortify their applications against potential attacks. As mobile technologies continue to advance, staying vigilant and proactive in addressing security concerns is essential to ensure the safety and integrity of mobile applications in the digital age.


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